Various types of plastic container bags utilize a pair of closure strips respectively having male and female members which interlock together to close an open end of the container bags to seal its interior from the external environment. The strips and associated container side walls are typically each formed from thermoplastic material. The container side walls are usually formed by extrusion. A sheet of extruded material is folded, forming two walls, or the two walls are constructed as two separate panels which are then heat-sealed together along two or three edges to define the container and an open end along one side thereof. The closure strips are also usually formed by extrusion and then connected to the side walls of the container along the open end by heat-sealing or other suitable means to define what is known as a recloseable profile. The closure strips and container body may also possibly be formed as a single piece by extrusion.
Each closure strip is preferably coextruded with a web member which is heat-sealed or otherwise secured to one of the side walls of the container body. More specifically, with reference to FIG. 1, a first of these webs 10 has an extruded layer formed with an upper web portion 12 and a lower web portion 14 extending coextensive with a first closure strip 16 thereon. This closure strip 16 contains first locking members 18 projecting inwardly from an inner surface of the first web 10, between the upper and lower web portions 12,14, to matingly engage second locking members 20 defining a second closure strip 22 which is coextruded with a second web 24 also having an upper web portion 26 and a lower web portion 28. The first and second locking members 18,20 are either male or female, respectively, to mate with each other. The lower web portions 14,28 are heat-sealed to the upper edge of respective ones of the plastic side walls (not shown in detail) as is known. The upper web portions 12,26 project upwardly from their associated closure strips 16,22 to respectively define what are commonly known as a top or a consumer side web located between the recloseable profile and the open end of the container. Typically, these webs 12,26, also known as flanges, are formed to allow for finger gripping to enable the consumer to grasp both side walls and enable separation of the side walls by pulling them away from each other to facilitate unlocking of the recloseable profile.
Since the first and second aforementioned webs 10,24 are each preferably extruded to contain the locking members 18,20, it is conventional practice to blend what is known as a slip agent into the extrusion material. These slip agents are primary amides or other materials known as slip agents in film extrusion which tend to migrate onto the profile surface over time to lubricate the locking members 18,20 and thereby to facilitate repeated locking and unlocking of these members during consumer usage. This slip agent is important to enable the male and female locking members 18,20 to deflect past each other during locking/unlocking. However, as a result of this slip agent being incorporated into the extrudate, the primary amides will also migrate or `bloom` onto the surfaces of the upper as well as the lower gripping webs 12,26 and 14,28. This prevents consumers from being able to write on these upper webs with a ballpoint pen to label or identify the package contents since the pen ink does not readily adhere to the slippery surfaces of the webs created by this slip agent.
It is accordingly one object of the present invention to enable a consumer to write on the upper web or consumer side web of a recloseable profile with a writing instrument to label or identify the package contents.
Another object is to allow the consumer to write on the upper web with a ballpoint pen.
Still another object is to enable the consumer to write on either the inside surface or the outside surface of each upper web and package side webs 14,28.
Yet a further object is to create a roughened writing surface in the upper webs, on the inside and/or outside surfaces, while allowing a slip agent to be added to vital areas in the locking members of the closure strips to aid in the ease of reclosing of the profile.
Yet a further object is to provide a roughened writing surface in the upper webs through the addition of an anti-slip agent which is uniformly mixed into the extrusion material which avoids the need for separate reservoirs and transfer channels and slot combining regions in a closure profile melt feed reservoir of a melt extrusion die apparatus.